Fire resistant foam and foam products, method and dispersions for making same

ABSTRACT

A synthetic polymer foam is produced which incorporates fine particles of expandable graphite which surprisingly impart excellent fire resistant properties to the foam, particularly to foam made with a non-halogenated hydrocarbon as the primary blowing agent. For best results, the foam is produced through mixing the constituent materials, including the expandable graphite using a screw extruder. The foam can also be produced by creating a graphite/polyol or graphite/isocyanate dispersion in an extruder then mixing the remaining components in a conventional batch mixing or high pressure spraying process. Alternatively, conventional mixing can be used for the entire process, but use of a screw extruder in whole or in part is preferred.

[0001] This application claims priority from U.S. ProvisionalApplication No. 60/192,231, filed Mar. 27, 2000.

[0002] The present invention relates to foam and foam products havingexcellent fire resistance achieved through the use of expandablegraphite. In particular, the foam is preferably made using smallparticles of expandable graphite and a non-halogenated hydrocarbon as aprimary blowing agent in an extrusion process. In preferred embodiments,rigid polyisocyanurate foam is made with expandable graphite particleshaving an average particle size less than 200 microns which exhibitsself extinguishing properties and good insulation qualities.

BACKGROUND

[0003] Foams and processes for their production are well known in theart. Such foams are typically produced by reacting ingredients such as apolyisocyanate with an isocyanate reactive material such as a polyol inthe presence of a blowing agent.

[0004] Synthetic foams have many uses and are produced in many forms.Rigid foam insulation panels are used in the construction of buildings.Foam bun stock is used for freezer insulation. Flexible foam is used inthe manufacture of automobiles and furniture. Shaped foam products areused for building facades and ornamental effects for both interior andexterior uses.

[0005] Foam products are generally highly flammable when made solely outof their basic components. A variety of materials have been used in thepast for imparting fire resistance to foams. For example, standardliquid flame retardants such as TRIS (-chloro-2-propyl) phosphateproducts, commercially available as ANTI-BLAZE 80 from Albright andWilson and as PCF from Akzo Nobel have been conventionally used toincrease the fire resistance of the foam. Such additives can be used toproduce Factory Mutual Class 1 rated foam when organic halogenatedhydrocarbons, such as 1,1-dichloro-1-fluorethane (HCFC-141b) are used asthe primary blowing agent. However, similar foams made withnon-halogenated hydrocarbons, such as iso-pentane and/or cyclopentane,used as the primary blowing agent fail to produce Factory Mutual Class 1rated foam.

[0006] The use of expandable graphite as a fire retardant for polymerfoams is generally known through the teaching of U.S. Pat. No.3,574,644. It has been shown that particle size has an impact on theeffectiveness of expandable graphite as a fire retardant. For example,U.S. Pat. No. 5,169,876 teaches the effective use of expandable graphitein a flexible polyurethane foam with a particle size of 300 to 1000microns, but that use of expandable graphite having a particle size ofless than 200 microns is ineffective.

[0007] It is desirable to produce foam and foam products having improvedfire resistance and/or self extinguishing characteristics. Since the useof certain halogenated hydrocarbons may have detrimental environmentaleffects, it is also desirable to provide foam made with anon-halogenated hydrocarbon as the primary blowing agent.

SUMMARY

[0008] A synthetic polymer foam is produced which incorporates fineparticles of expandable graphite which surprisingly impart excellentfire resistant properties to the foam, particularly to foam made with anon-halogenated hydrocarbon as the primary blowing agent. For bestresults, the foam is produced through mixing the constituent materials,including the expandable graphite using a screw extruder. The foam canalso be produced by creating a graphite/polyol or graphite/isocyanatedispersion in an extruder then mixing the remaining components in aconventional batch mixing or high pressure spraying process.Alternatively, conventional mixing can be used for the entire process,but use of a screw extruder in whole or in part is preferred.

[0009] Expandable graphite material having an average particle size ofless than 200 microns, such as expandable graphite commerciallyavailable as GRAFGuard 160-80 (80 mesh, 177 microns) from UCARGraph-Tech Inc., wherein sulfuric acid and nitric acid are encapsulatedwithin the graphite can be used. A neutral grade of expandable graphitehaving a PH of at least 5, preferably 7, with an expansion threshold of160° C., such as GRAFGuard 160-80 N, is preferred. Expandable graphitewith very fine average particle size of 100 microns or less, such asGRAFGuard 160-150 N (150 mesh), can be used with a non-halogenatedhydrocarbon blowing agent when employing an extruder to make rigidPUR/PIR foam. Preferably the foam formulation includes at least 1%loading of expandable graphite to produce a fire resistant foam and atleast 3% loading to produce self extinguishing foam and foam products.When subjected to burning, the expandable graphite particles within thefoam expand up to one hundred times the original diameter creating agraphite char that retains an excellent heat resistance in addition toproviding self extinguishing properties.

[0010] Applicants have discovered that use of a unique combination ofexpandable graphite and carbon black produces an excellent foam producthaving both fire resistance and good insulating qualities, even wherenon-halogenated hydrocarbon blowing agents are employed in themanufacture of the foam.

[0011] It is an object of the present invention to provide foam and foamproducts having improved fire resistance.

[0012] It is a further object to provide various methods for making suchfoams including the use of an extruder and the use of non-halogenatedhydrocarbon blowing agents.

[0013] It is a further object to employ small particle size expandablegraphite and/or carbon black in the manufacture of such foam.

[0014] Other objects and advantages of the present invention will becomeapparent through a description of the presently preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWING(S)

[0015]FIG. 1 is a schematic illustration of an apparatus for extrudingpolymer foam, or dispersions for use in making such foam, in accordancewith the teachings of the present invention.

[0016]FIG. 2 is a cross-sectional side view of the extruder head of theextruder of FIG. 1.

[0017]FIG. 3 is a table reflecting a control example made withoutexpandable graphite and with a non-halogenated hydrocarbon blowingagent.

[0018]FIG. 4 is a table of three foam examples made in accordance withthe teachings of the present invention.

[0019]FIG. 5 is a table reflecting foam characteristics of the examplesset forth in FIGS. 3 and 4.

[0020]FIG. 6 is a table reflecting additional examples of extruder madeisocyanurate foam reflecting control Example 5 and Examples 6 and 7 madein accordance with the teachings of the present invention.

[0021]FIG. 7 is a table reflecting foam characteristics of the examplesset forth in FIG. 6 in comparison with additional prior art examples.

[0022]FIG. 8 is a table of preferred boardstock formulations.

[0023]FIG. 9 is a table of preferred bunstock formulations.

[0024]FIG. 10 is a table of preferred dispersion formulations.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

[0025] Foams in accordance with the present invention are preferablymanufactured using an extruder, such as the extruder system 102schematically illustrated in FIG. 1. The extruder can be used for theentire process or to make a dispersion of expandable graphite and/orcarbon black which is then used to make foam using any mixing method.Use of the extruder provides the best results, but other conventionalmixing methods may be used.

[0026] The extrusion system 102 includes a single or twin screw extruder104 and an associated reservoir system 106. The extruder 104 includes aseries of barrels C1-C12 and an extruder head 120. Preferably a twinscrew extruder is employed such as described in U.S. Pat. No. 5,723,506assigned to the assignee of the present invention.

[0027] The reservoir system 106 includes a plurality of reservoirs150-156 from which the foam components are supplied. The reservoirs150-156 feed the foam component materials to the barrels C1-C12 and head120 of the extruder 104 via a network of feed lines and valves asillustrated.

[0028] In manufacturing foam using the extrusion system of FIG. 1,expandable graphite particles are preferably provided to the extruder104 at barrel C1 from a fill station 150. Additional expandable graphiteand/or carbon black is preferably provided to the extruder 104 at barrelC4 from a fill station 152. Isocyanate solution is preferably mixed andfed to barrels C2 and C6 of the extruder 104 from reservoirs 151 and153. The isocyanate solution may be optionally pre-mixed with adispersing agent and/or surfactant at reservoirs 151 and 153 andprovided to the extruder 104 with the isocyanate at barrels C2 and C6.

[0029] Polyol is preferably provided from a reservoir 155 and fed to theextruder 104 at barrel C9. Surfactant, curing agent and foaming agent ispreferably pre-mixed with the polyol contained in the reservoir 155 andfed to the extruder 104 at barrel C9.

[0030] Foaming and/or blowing agents are preferably provided from areservoir 154 and fed to the extruder 104 at barrel C8 without previousmixing with other components. Additionally, foaming and/or blowingagents may be mixed with the polyol at reservoir 155 prior to entry tothe extruder 104 at barrel C9. For example, foaming agent is provided toextruder 104 at barrel C9 after the foaming agent is first mixed with apolyol/surfactant mixture.

[0031] Catalyst is preferably introduced into the extruder 104 via anextruder head 120 from reservoir 156. A cross-sectional side view of theextruder head 120 of the extrusion system is shown in FIG. 2.

[0032] In making foam, the mixture of the component parts of thegraphite particles, isocyanate, polyol, and additional materials,without the catalyst, arrives via a hose 200 (shown in FIG. 1) to anentry port 202 in a mixing block 204 of the extruder head 120. At mixingblock 204, the component mixture travels via a worm gear 206 to agitator208 located in a cavity area 210. Concurrently, catalyst enters at acatalyst port 214 and travels along a duct 215 to arrive in the cavityarea 210 via a catalyst entry port 216. The mixture of the componentparts of the expandable graphite isocyanate, polyol and additionalagents and catalyst are mixed together by agitator 208 in the cavityarea 210 and continues out of the cavity area 210, preferably onto aconveyor system such as the conveyor illustrated in U.S. Pat. No.5,723,506. Preferably, the cavity 210 is 2 to 3 inches wide and theagitator is rotated at approximately 3500 to 5500 rpm.

[0033] A preferred method of manufacturing foam using the extruder ofFIG. 1 includes feeding graphite particles and/or carbon-black fromsource 150 to the extruder 104 at barrel C1. A mixture of isocyanate,dispersing agent and surfactant is fed to the extruder 104 at barrel C2from reservoir 151. Additional graphite particles and/or carbon-blackmay be added from source 152 and fed to the extruder 104 at barrel C4particularly, when loading of the graphite particles and/or carbon-blackis to exceed 12-15%. An additional mixture of isocyanate, dispersingagent and surfactant is then added to the extruder 104 at barrel C6 fromreservoir 153. Blowing agent is provided to the extruder 104 at barrelC8 from reservoir 154. Polyol, foaming and blowing agent, surfactant andcuring agent are fed to the extruder 104 at barrel C9 from reservoir155. Finally, a catalyst or catalyst mixture is provided to the extruderhead 120 from reservoir 156.

[0034] A preferred method of manufacturing an isocyanate dispersion inaccordance with the teachings of the present invention using theextruder of FIG. 1 includes feeding graphite particles and/or carbonblack from source 150 to the extruder 104 at barrel C1. A mixture ofisocyanurate and dispersing agent, optionally with surfactant, is fed tothe extruder 104 at barrel C2 from reservoir 151. Additional graphiteparticles and/or carbon black may be added from reservoirs 152 and fedto the extruder 104 at barrel C4. An additional mixture of isocyanurateand dispersing agent, optionally with surfactant, may then be added tothe extruder 104 at barrel C6 from reservoir 153. No polyol or catalystmaterials are added to the extruder and the resultant dispersion exitsthe extruder at the last barrel C12 and is preferably directed into anappropriate container, bypassing the extruder head 202.

[0035] A preferred method of manufacturing a polyol dispersion inaccordance with the present invention using the extruder of FIG. 1includes feeding graphite particles and/or carbon black from source 150and/or source 152 to the extruder 104 at barrel C1 and/or barrel C4. Amixture of polyol and a dispersing agent optionally with foaming agent,blowing agent, surfactant and/or curing agent, is fed to the extruder104 at barrel C9 from reservoir 155. The polyol dispersion exits theextruder at barrel C12, preferably directly into an appropriatecontainer, bypassing the extruder head 202.

[0036] The production of foams based on isocyanates is known per se andis described, for example, in German Offenlegungsschriften 1,694,142,1,694,215 and 1,720,768, as well as in Kunststoff-Handbuch [PlasticsHandbook], Volume VII, Polyurethane, edited by Vieweg and Hochtlen, CarlHanser Verlag, Munich 1966, and in the new edition of this tome, editedby G. Oertel, Carl Hanser Vedag, Munich, Vienna, 1983.

[0037] These foams are mainly those that comprise urethane and/orisocyanurate and/or allophanate and/or uretdione and/or urea and/orcarbodiimide groups. Preferred starting components include aliphatic,cycloaliphatic, araliphatic, aromatic and heterocyclic polyisocyanates,such as those described, for example, by W. Siefken in Justus LiebigsAnnalen der Chemie, 562, pp. 75-136, for example, those of the formula

Q(NCO)_(n)

[0038] in which n denotes 2-4, preferably 2-3, and Q denotes analiphatic hydrocarbon radical of 2-18, preferably 6-10 carbon atoms, acycloaliphatic hydrocarbon radical of 4-15, preferably 5-10 carbonatoms, an aromatic hydrocarbon radical of 6-15, preferably 6-13 carbonatoms or an araliphatic hydrocarbon radical of 8-15, preferably 8-13carbon atoms, for example, such polyisocyanates as described in DE-OS2,832,253, pp. 10-11.

[0039] Particularly preferred are usually those polyisocyanates whichare technically readily accessible, for example, the 2,4- and2,6-toluylene diisocyanate as well as any mixture of these isomers(“TDI”); polyphenyl5 polymethylenepolyisocyanates, such as thoseobtained by an aniline formaldehyde condensation and subsequenttreatment with phosgene (“crude MDI”), and polyisocyanates comprisingcarbodiimide groups, urethane groups, allophanate groups, isocyanurategroups, urea groups or biuret groups (“modified polyisocyanates”),especially those modified polyisocyanates which are derived from 2,4-and/or 2,6-toluylene diisocyanate and from 4,4′- and/or2,4′-diphenylmethane diisocyanate.

[0040] The starting components may further be compounds of a molecularweight usually of 400 to 10,000, containing at least two hydrogen atomsreactive toward isocyanates. These comprise, besides compoundscontaining amino, thio, or carboxyl groups, preferably compoundscontaining hydroxyl groups, in particular compounds containing 2 to 8hydroxyl groups, especially those of a molecular weight of 1,000 to6,000, preferably 2,000 to 6,000, for example polyethers and polyestersas well as polycarbonates and polyester amides containing at least 2,usually 2 to 8, preferably 2 to 6 hydroxyl groups; these compounds areknown per se for the preparation of homogenous and cellularpolyurethanes and are disclosed, for example in DE-OS 2,832,253, pp.11-18.

[0041] When appropriate, compounds comprising at least two hydrogenatoms reactive toward isocyanates and of a molecular weight of 32 to 399may be used as further starting components. Also, in this case,compounds containing hydroxyl groups and/or amino groups and/or thiolgroups and/or carboxyl groups, preferably compounds containing hydroxylgroups and/or amino groups, are understood to be those which are used aschain lengtheners or crosslinking agents. These compounds usually have 2to 8, preferably 2 to 4 hydrogen atoms reactive toward isocyanates.Appropriate examples are disclosed in DE-OS 2,832,253, pp. 19-20. Otherexamples of polyisocyanates and polyols useful in the invention aredescribed in U.S. Pat. No. 5,149,722, co-owned by the assignee of thepresent invention and incorporated herein by reference as if fully setforth.

[0042] Blowing agents which may be used to make foam include waterand/or readily volatile inorganic or organic substances and otherauxiliary volatile blowing agents typically used to blow PUR/PIR foams.Water, however, used in small quantities serves as a foaming agent whereother blowing agents are used.

[0043] Organic blowing agents include acetone, ethylacetate;halogen-substituted alkanes, such as methylene chloride, chloroform,ethylidene chloride, vinylidene chloride, monofluoro trichloromethane,chlorodifluoromethane, dichlorodifluoromethane, dichlorodifluoroethane,dichlorotrifluoroethane; also halogenated and non-halogenatedhydrocarbon blowing agents.

[0044] Specific examples of non-halogenated hydrocarbon blowing agentsinclude: pentane, butane, hexane, heptane, diethyl ether, isopentane,n-pentane and cyclopentane.

[0045] Specific examples of halogenated hydrocarbon blowing agentsinclude: 1,1,1,4,4,4-hexafluorobutane (HFC-356); 1,1-dichloro-1fluoroethane (HFC-141/b); the tetrafluoroethanes such as1,1,1,2-tetrafluoroethane (HFC-134a); the pentafluoropropanes such as1,1,2,2,3 pentafluoropropane (HFC-245ca), 1,1,2,3,3-pentafluoropropane(HFC 245ea), 1,1,1,2,3-pentafluoropropane (HFC-245eb), and 1,1,1,3,3pentafluoropropane (HFC-245fa); the hexafluoropropanes such as1,1,2,2,3,3-hexafluoropropane (HFC-236ca), 1,1,1,2,2,3-hexafluoropropane (HFC-236cb), 1,1,1,2,3,3-hexafluoro-propane (HFC-236ea),1,1,1,3,3,3-hexafluoropropane (HFC-236fa); the pentafluorobutanes suchas 1,1,1,3,3-pentafluorobutane (HFC-365); and difluoroethanes such as1,1-difluoroethane (HFC-152a).

[0046] Inorganic blowing agents are, for example, air, CO₂ or N₂O. Ablowing effect may also be obtained by adding compounds which decomposeat temperatures above room temperature giving off gases, such asazodicarbonamide or azoisobutyronitrile. Other examples of blowingagents may be found in Kunststoff-Handbuch, Vol. VII, by Vieweg andHochtlen, Carl-Hanser Verlag, Munich, 1966, on pages 108 and 109, 453 to455 and 507 to 510.

[0047] Different types of blowing agents are used in combination, butuse of a non-halogenated hydrocarbon chemical as the primary blowingagent has generally been avoided due to the flammability of foams whichconventionally result. Use of expandable graphite as taught by thepresent invention permits the use of a non-halogenated primary blowingagent in the production of foam which is rated as Factory Mutual Class 1when tested using test method ASTM E84.

[0048] When appropriate, other auxiliary agents and additives may beused at the same time, such as:

[0049] water and/or other highly volatile organic substances aspropellants, i.e. foaming agents;

[0050] additional catalysts of the type known per se in amounts up to10% by weight of the polyol component;

[0051] surface-active additives, such as emulsifiers and foamstabilizers, and

[0052] reaction retardants, for example acidic substances such ashydrochloric acid or organic acid halides, also cell regulators of thetype known per se, such as paraffins or fatty alcohols ordimethylpolysiloxanes, as well as, pigments or dyes and other flameretardants of the type known per se, for example tricresyl phosphate,also stabilizers against the effect of aging and weathering,plasticizers and fungistats and bacteriostats as well as fillers such asbarium sulphate, kieselguhr, carbon black, expanded or expandablemicrospheres or whiting.

[0053] Other examples of surface active additives, foam stabilizers,cell regulators, reaction retardants, stabilizers, flame retardants,plasticizers, dyes, fillers, fungistats, bacteriostats to be used at thesame time if appropriate, as well as details concerning the use andaction of these additives are described in Kunststoff-Handbuch [PlasticsHandbook], Volume VII, edited by Vieweg and Hochtlen, Carl HanserVerlag, Munich 1966, for example on pages 103-113.

[0054] FIGS. 3-5 reflect various foams, Examples 1-4, made in accordancewith the extrusion method recited above. A non-halogenated hydrocarbonblowing agent, pentane, was the blowing agent used in all Examples 1-4.

[0055] Example 1 reflects a control example with no expandable graphitematerial. By comparison, the other examples were made with differingamounts of expandable graphite having an average particle size of lessthan 200 microns. Burn tests were performed with the control foam,Example 1, and expandable graphite foams, Examples 2-4. Thickness andweight loss examples were measured.

[0056] Visually, polyisocyanurate foam made with the non-halogenatedblowing agent and a 5% loading or higher of expandable graphite,Examples 2-4, produced no noticeable black smoke as withpolyisocyanurate made with the non-halogenated blowing agent and astandard liquid flame retardant, Example 1. There was no significantdensity increase using expandable graphite in the range of 5%-12%. Therewas also considerably less flame spread noticed during the bum with 5%or more of graphite particles.

[0057] Based on the test results, it was determined that fire retardantfoams can be produced by providing 1% to 50% by weight evenly dispersedexpandable graphite particles which have an average particle size ofless than 200 microns. Moreover, the use of such expandable graphite ina preferred range of 3%-20% by weight can produce a class 1 rated foamper Factory Mutual Standard F.M. 4450 and Underwriters LaboratoriesStandard UL1256 when tested using test method ASTM E84.

[0058] Tables 6-7 reflect an additional comparative analysis, Examples5-7, of a control versus two example foams made in accordance with theteachings of the present invention. Control Example 5 contained noexpandable graphite. Example 6 contained expandable graphite and Example7 contained a combination of expandable graphite and carbon black. Inall cases, the primary blowing agent was a non-halogenated hydrocarbonchemical. Less than 1% of a halogenated hydrocarbon co-blowing agent andless than 1% water serving as a foaming agent were used in Examples 6and 7.

[0059] As reflected in Table 7, the foam made in accordance with Example7 had the best K factor and was otherwise comparable to prior artcommercial foam, Foam II, made with a halogenated hydrocarbon blowingagent. The foam made in accordance with Example 6 had a K factor betterthan the prior art competitive foam, Foam I, made with a non-halogenatedprimary blowing agent, but not quite as good as the prior art foam, FoamII, made with a non-halogenated primary blowing agent. However, unlikethe prior art foam made with a non-halogenated primary blowing agent,Foam I, the Example 6 foam passed Factory Mutual Standard F.M. 4450 andUnderwriter's Laboratory Standard UL1256 for a Class 1 rating whentested in accordance with Test Method ASTM E84.

[0060] Based on the results of Examples 2, 3, 4 and 6, it is believedthat the Example 7 foam will also be accorded a Factory Mutual Class 1rating when independently tested in accordance with Test Method ASTME84.

[0061] In accordance with the experimentation and testing performed bythe present inventors, preferred formulations for the manufacturer ofPUR/PIR boardstock and bunstock are set forth in FIGS. 8 and 9,respectively. While prefered types and/or sources of the componentmaterials are identified, these are non-limiting examples. Various otheradditive materials as discussed above, preferably not exceeding 100parts by weight, may be added to the formulations set forth in FIGS. 8and 9. These PIR/PUR foam formulations are primarily characterized inthe use of at least 3% expandable graphite preferably having an averageparticle size less than 200 microns, the use of a non-halogenatedhydrocarbon chemical or blend as the primary blowing agent, and the useof less than 1% of a halogenated blowing agent. The use of at least 4.5%expandable graphite and 3.5% carbon black can produce a class 1 ratedfoam per Factory Mutual Standard F.M. 4450 and Underwriters LaboratoriesStandard ULL1256 when tested using test method ASTM E84.

[0062] Preferably, the components are combined by the use of an extruderas set forth above. Alternatively, the components can be mixed utilizingother methods. Where conventional mixing is employed, it is preferred tocreate either a polyol or isocyanate dispersion with the expandablegraphite and optionally carbon black which is then used to make foam inaccordance with the formulations set forth in FIGS. 8 and 9.

[0063]FIG. 10 sets forth preferred dispersion formulations in thisregard. Dispersions so made can be stored and/or shipped to otherlocations with minimal effect on the uniformity of the distribution ofthe expandable graphite particles in the dispersion. This permits asingle extruder to supply many batch processing facilities to make foamin accordance with one of the preferred methods taught by the presentinvention.

What is claimed is:
 1. A rigid polyurethane and/or polyisocyanurate foamhaving fire resistance comprising: from 1-50% by weight of evenlydispersed expandable graphite particles having an average particle sizeless than 200 microns and from 99 to 50% by weight of a closed cellpolyurethane foam.
 2. A rigid polyurethane or polyisocyanurate foamaccording to claim 1 wherein the expandable graphite particles comprise3 to 20% by weight of the foam and have a PH greater than
 5. 3. The foamof claim 2 which passes the burning test of Factory Mutual Standard F.M.4450 and Underwriters Laboratories standard UL 1256 for class I ratingswhen tested in accordance with test method ASTM E84.
 4. A rigidpolyurethane or polyisocyanurate foam according to claim 1 having atleast 4.5% by weight expandable graphite particles and at least 3.5% byweight carbon black.
 5. The foam of claim 4 which passes the burningtest of Factory Mutual Standard F.M. 4450 and Underwriters Laboratoriesstandard UL 1256 for class 1 ratings when tested in accordance with testmethod ASTM E84.
 6. The foam according to claim 2 wherein the expandablegraphite particles are GRAFguard 160-80-N expandable graphite.
 7. Apolyurethane and/or polyisocyanurate foam having fire resistance madeusing at least 3% by weight expandable graphite and a non-halogenatedhydrocarbon chemical or a non-halogenated hydrocarbon chemical blend asa primary blowing agent.
 8. The foam according to claim 7 wherein theexpandable graphite particles are GRAFguard 160-80-N expandablegraphite.
 9. The foam according to claim 7 wherein the primary blowingagent is selected from the group consisting of pentane, butane, hexane,heptane, diethyl ether, isopentane, n-pentane and cyclopentane or blendsof chemicals from said group.
 10. A rigid polyurethane and/orpolyisocyanurate foam made according to claim 7 by mixing: 10.57 to41.14 PBW expandable graphite particles having an average particle sizeless than 200 microns; 191 to 400 PBW isocyanate; 75 to 125 PBW polyol;16 to 36 PBW of a non-halogenated hydrocarbon chemical or anon-halogenated hydrocarbon chemical blend as a primary blowing agent; 0to 20.57 PBW of carbon black; and 19 to 165 PBW other ingredients withless than 1% by weight of halogenated blowing agents.
 11. The foam ofclaim 10 which passes the burning test of Factory Mutual Standard F.M.4450 and Underwriters Laboratories standard UL 1256 for class 1 ratingswhen tested in accordance with test method ASTM E84.
 12. A rigidpolyurethane and/or polyisocyanurate foam made according to claim 7 bymixing: 14 to 40 PBW expandable graphite particles having an averageparticle size less than 200 microns; 192 to 500 PBW isocyanate; 75 to125 PBW polyol; 5 to 46 PBW of a non-halogenated hydrocarbon chemical ora non-halogenated hydrocarbon chemical blend as a primary blowing agent;0 to 20 PBW of carbon black; and 20 to 155 PBW other ingredients withless than 1% by weight of halogenated blowing agents.
 13. The foam ofclaim 12 which passes the burning test of Factory Mutual Standard F.M.4450 and Underwriters Laboratories standard UL 1256 for class 1 ratingswhen tested in accordance with test method ASTM E84.
 14. A method forfacilitating the manufacture of fire resistant polyurethane and/orpolyisocyanurate foam comprising: introducing 10.57 to 41.14 PBWexpandable graphite particles having an average particle size less than200 microns to the screw of an extruder; introducing at least 2 PBW of adispersing agent to the screw of the extruder; and using the screw ofthe extruder to mix the expandable graphite particles and dispersantwith either 191 to 500 PBW of a isocyanate or 75 to 125 PBW of a polyol.15. The method of claim 14 wherein 95 to 105 PBW of polyol areintroduced to the screw of the extruder; 14 to 32 PBW of the expandablegraphite particles are introduced to the screw of the extruder; 0 to 16PBW of carbon black is introduced to the screw of the extruder; 3 to 4PBW of the dispersing agent is introduced to the screw of the extruder;and 0 to 50 PBW of other non-reactive ingredients are introduced to thescrew of the extruder to produce a polyol dispersion.
 16. The methodaccording to claim 14 wherein 231 to 251 PBW of isocyanate is introducedto the screw of the extruder; 14 to 32 PBW of the expandable graphiteparticles are introduced to the screw of the extruder; 0 to 16 PBW ofcarbon black is introduced to the screw of the extruder; and 3 to 4 PBWof the dispersing agent is introduced to the screw of the extruderextruder; and 0 to 100 PBW of other non-reactive ingredients areintroduced to the screw of the extruder to produce an isocyanatedispersion.
 17. The method according to claim 14 wherein: 10.57 to 41.14PBW of expandable graphite particles having an average particle sizeless than 200 microns are introduced to the screw of the extruder; 191to 400 PBW of isocyanate is introduced to the screw of the extruder; 75to 125 PBW of polyol is introduced to the screw of the extruder; 16 to36 PBW of a non-halogenated hydrocarbon chemical or a non-halogenatedhydrocarbon chemical blend as a primary blowing agent is introduced tothe screw of the extruder; 0 to 20.57 PBW of carbon black are introducedto the screw of the extruder; and 19 to 165 PBW other ingredients withless than 1 PBW of halogenated blowing agents are introduced to thescrew or an extrusion head of the extruder to produce rigid foamboardstock.
 18. The method according to claim 14 wherein: 14 to 40 PBWof expandable graphite particles having an average particle size lessthan 200 microns are introduced to the screw of the extruder; 192 to 500PBW isocyanate to is introduced to the screw of the extruder; 75 to 125PBW polyol is introduced to the screw of the extruder; 5 to 46 PBW of anon-halogenated hydrocarbon chemical or a non-halogenated hydrocarbonchemical blend as a primary blowing agent is introduced to the screw ofthe extruder; 0 to 20 PBW of carbon black is introduced to the screw ofthe extruder; and 20 to 155 PBW other ingredients with less than 1% byweight of a halogenated blowing agent are introduced to the screw or anextrusion head of the extruder to produce rigid foam bunstock.